The present invention relates to a carriage device of a floppy disk apparatus, for supporting a magnetic heads.
In a floppy disk apparatus, a magnetic head performs a seek operation on a magnetic recording medium, so as to find a desired track, and once found performs a data read/write operation thereon. The magnetic head is placed on a carriage, and the carriage is linearly moved- to enable the magnetic head to perform the seek operation. Normally, the carriage has a pair of parallel arms, and magnetic heads are mounted on the distal ends of the respective arms. These heads oppose each other at a predetermined interval.
A carriage has recently been developed which is made of a resin material such as polycarbonate filled with glass. This is because a disk apparatus can be made light in weight and because a resin material is easy to work. On the other hand, a resin material has a relatively high thermal expansion coefficient and high hygroscopicity. Consequently, the carriage tends to contract or expand when changes occur in temperature and humidity. When the carriage contracts or expands, the position of the magnetic heads is displaced, thereby degrading the positioning accuracy of the magnetic heads during the seek operation, and resulting in an erroneous operation. In recent years especially, since the interval between tracks has been greatly decreased, in order to increase the recording density of the magnetic recording medium, the merest expansion or contraction can adversely affect the positioning accuracy of the magnetic head.
In addition, when one of the pair of arms of the carriage expands or contracts different rate than the other, the interval between the magnetic heads thus varies and poses the same problem as described above.